Production and separation of isomeric isopropylnaphthalenes



April J. E. NICKELS PRODUCTION AND SEPARATION OF ISOMERIC ISOPROPYLNAPHTHALENES Filed July 8, 1948 TTOPNEY Patented Apr. 15, 1952 PRODUCTION AND SEPARATION F ISO- MERIC ISOPROPYLNAPHTHALENES Joseph E. Nickels, Pittsburgh, Pa., assigner to Koppers Company, Inc.. Pittsburgh, Pa., a corporation of Delaware Application July 8, 1948, Serial N0.`37,549

Claims.

This invention relates to alphaand beta-isopropylnaphthalenes. More particularly the invention relates to a process of producing pure alphaand pure beta-isopropylnaphthalenes I have found that naphthalene may be alkylated with propylene in liquidY phase in the presence of an alumina-silica catalyst at a temperature of 250 C. with a liquid hourly spaced velocity of about 2` and a molar ratio of naphthalene to propylene of 5:1. This temperature may be varied from 150 to 350 C. in accordance with the space velocity and the molar ratio may vary from three to iive parts of naphthalene to one partV of propylene.

'I'his alkylation produces a mixture of alphaand beta-isopropylnaphthalenes which naphthalenes have very closely related boiling points and form a eutectic mixture with each other so thaty it is very hard to separate these two compounds. Further the alpha-isopropylnaphthalenehas not been separated from the mixture heretofore `because the alpha-isopropylnaphthalene is generally formed in a. minor proportion and cannot beseparated as such by crystallization `or distillation.

`The mixture of alphaand beta-isopropylnaphthalene is'a solventfor use inthe synthesis ofaromaticvcompoundsbut the two isomers must be. separated to use them as intermediate products in the manufactureof` dyestuffs which involve hydroxyalkylation and/or sulphonation.

The. primary object of the present invention is izo-:provide a process of separating the mixture of. alphaand 1beta-isopropylnaphthalene isomers as substantially pure products.

f .Another object of the invention is to provide aA process `by which the pureV isopropylnaphthalenes maybe separated fromaeutectic mixture of alphaand beta-isopropylnaphthalenes.

With these and other objects in View, the invention consists in the process of producing pure alphaand beta-isopropylnaphthalenes from a mixture of these products.

In the drawing is illustrated a flow sheet of an apparatus in which the preferred form of the invention may be carried out.

Referring to the drawing, naphthalene is introduced through a pipe I0 and propylene is introduced `through a pipe I2. The propylene is dissolved in the naphthalene and they pass through` an-alkylator I4 under sufcient pressure (200 to 900` lbs. per square inch) to maintain the product in the liquid phase. The a1- kylator is lled with a bed` of granular catalyst consisting of an alumina. activated silica (1% to 25% alumina and 99 to '75% silica) at a tem-- perature of approximately 250 C. The preferred mixture consists of a molar' ratio ot naphthalene to propylene of 5:1. This molar ratio may vary from 3 to l0 parts of na'phthalene to 1 part of propylene and the temperature may `vary from 150 to 350 C. in accord-ance with the space velocity in the alkylator. At a temperature of 250 C. a space velocity of approxi-mately 2 is maintained. In the alkylator I4 a mixture of alphaand betaisopropylnaphthalenes together with unconverted naphthalene are formed and this mixture flows through a line I to a fractionating column I8 where it is distilled to pass overhead the uncnverted naphthalene. This naphthalene thenfiows through-a line back to the line I2. The alkylate'd isopropylnaphthalenes pass out of the bottom of fractionator I8 through a. line 2-2 into the mid portion of fractionator 24 where a distillate composed of a mixture of alphaand beta-isopropylnaphthalene passes overhead through a line 25 into dehydrogenation converter 2.8. Water or steam` is added to thel mixture of alphaand beta-isopropylnaphthalenes through a line 30 and this mixture then. passes in the vapor phase through a catalyst bed composed of a granular catalyst which maybe a calcined limestone or dolomite, or a ferri-ferons limestone, or a 1-707 catalyst" which is composed of magnesium oxide, iron oxide, copper oxide and KzO, or a zinc catalyst composed of substantially of ZnO, 5% CuO; It hasA been found that 5% KZO' and 5% FezO'a. thel 1707 Catalyst is very reactive and therefore causes decomposition of. the reaction product-s or the formation of secondary reaction products. The `preferred catalyst is the calcined limestone or dolomite.

The vapor phase mixture passing through the converter 28 is maintained at a temperature of 550'o to 700 C. and at substantially atmospheric pressure. alphaand beta-isopropylnaphthalenes is dehydrogenated to a mixture of alphaand betaisopropenylnaphthalenes. The reaction products from the converter 28 pass into a separator 30 where gases are removed through a line` 32 and water is drawn ofi at 34. The 'mixture oi alphaand beta-isopropenylnaphthalenes hows through a line 36 into a fractionator 38 where it is distilled to take overhead naphthalene, methylnaphthalene and ethylnaphthalene, through a line 40. The mixture of alphaand beta-isopropenylnaphthalenes flows through a line 4:2 from the still 38 into a fractionatng still 4A.

In the converter 28, the mixture of In the fractionating still 44 alpha-isopropenylnaphthalene is taken overhead. through a line 46 and a mixture of beta-isopropenylnaphthalene and isopropylnaphthalenes ows through a line 48 to fractionating still 58. In the fractionating still 50 the isopropylnaphthalenes mixture is taken overhead through a line 52 and passed back to the dehydrogenator 28. The mixture then freed of alphaand beta-isopropylnaphthalenes is taken through a line 54 to a fractionator 56 where the beta-isopropenylnaphthalene is taken overhead through a line 58 and a higher boiling point residue removed from the bottom of the still through a line 60. The alpha-isopropenylnaphthalene from the line 46 flows through a line 62 to a hydrcgenator 64. The hydrogenator is lled with a granular catalyst composed of metallic nickel deposited on a refractory material such as bauxite or pumice, hydrogen being added to the alpha-isopropenylnaphthalene through a line 66. The alpha-isopropenylnaphthalene is hydrogenated at a temperature of 150 C. or less at a pressure of 300 to 2000 lbs. per square inch to produce alpha-isopropylnaphthalene. The alpha-isopropylnaphthalene with other reaction products, then passes to a still 68 through a line 10 where it is fractionated to take'overhead a pure alpha-isopropylnaphthalene through a line 72.

The beta-isopropenylnaphthalene from line 58 passes through a line` 14 to a hydrogenator 16, hydrogen being introduced into the line I4 through a line 18. The hydrogenation of the beta-isopropenylnaphthalene is carried out at substantially the same temperature and pressure conditions used in the hydrogenation of the alpha-isopropenylnaphthalene. Pure beta-isopropylnaphthalene flows from the hydrogenator 16 through a line 'I9 into a fractionator 80 and pure beta-isopropyln-aphthalene is taken overhead through a, line 82.

Substantially pure beta-isopropylnaphthalene may be recovered from the mixture of alphaand beta-isopropylnaphthalenes coming overhead from the fractionator 24 through the line 26. If it is desired, this mixture may be passed through a line 84 into a dilution and refrigeration tank 86 where it is diluted with an equal volume of methyl alcohol and then cooled to a temperature of about 35 to 40 C. to crystallize a substantially pure beta-isopropylnaphthalene The crystallized beta-isopropyl naphthalene and mother liquor may then be removed from the cooler 86 and passed into a separator 88 to separate the mother liquor from the crystallized betaisopropyl naphthalene. The separation may be eiected by any means customarily employed in separating crystals from mother liquor in a crystallization process. The mother liquor separated may then flow through a line 90 back to the line 26 and into the dehydrogenator 28 for further treatment. A substantial amount of beta-isopropyl naphthalene will be present with the alpha-isopropyl naphthalene and these two products in purii'led form will be separated in the apparatus as described above.

In place of methanol which is the low boiling solvent to be used in the crystallization separation of beta-isopropylnaphthalene, petroleum ethers and paraiin hydrocarbons containing 3 to 7 carbon atoms may be used.

By the above process pure alphaand betaisopropylnaphthalenes may be obtained which are very useful as intermediate products in the manu- ISOPROPYLNAPHTHALENE DEHYDROGENATION Experimental Conditions:

Catalyst used H2O:HC ratio, moles Catalyst temp., C Length of run, hrs Product Distribution, weight per cent:

Gases Naphthalene Methylnaphthalenes. Ethylnaphthalenes.. Vinylnaphthalenes-; Isopropylnaphthalenes Isopropenylnaphthalcnes Residue Carbon (as CO1 and CO carbon deposited on catalyst) Composition of Gases, vol. per cent:

Hydrogen-- Ethylene.. Paraiiins.- Paran index Isopropenylnaphthalene Yields, weight per cent:

Ultimate Per pass The isopropylnaphthalenes from the run at Y 600 C. was fractionated to give a cut below 150 C. composed of naphthalene, methyl-naphthalene and ethyl-naphthalene. The next cut from 150 to 162 C. is composed of alpha-isopropenylnaphthalene, the fractionation being carried out at 50 mm. of mercury in a 23 plate column; the cut from 162 to 168 C. was 'composed of alphaand beta-isopropylnaphthalenes; and the cut from 168 to 180 C. was composed of beta-isopropenylnaphthalene- The material boiling above 180 C. was discarded as residue. The dehydrogenation at 600 C. gave approximately 10% yield of alpha-isopropenylnaphthalene. On the other hand when using lime or dolomite, a yield of a mixture of alphaand beta-isopropenylnaphthalenes of about is obtained oi'which alpha-isopropenylnaphthalene is approximately 12%, the remainder being beta-isopropenylnaphthalene. When these isopropenyl isomers are hydrogenated a substantial recovery of pureV alphaand beta-isopropylnaphthalenes can 4be obtained.

The preferred form of the invention having been thus described, what is claimed as new is:

1. A process of producing substantially purealphaand beta-isopropyl naphthalenes from al mixture thereof suchas is obtained by: alkylating naphthalene under highl pressure in thepres-VV ence of an excess of propylene in liquid phase at a temperature of to 300 C.in thep'resence of an activated alumina-'silica catalyst compris-e ing: dehydrogenating the mixture of alpha-and beta-isopropyl naphthalenes non-destructively 'to produce a mixture of alphaand'beta-sopropenyl naphthalenes, distilling the mixture `to separate alphaand beta-isoprcnpenyl` naphthalenes and', separately hydrogenating the alphaand beta-- isopropenyl naphthalenes to recoverrespectivel'yf Furthermore the alphaand' alphaand beta-isopropyl naphthalenes, and purifying the alphaand beta-isopropyl naphthalene products separately by distillation 2. The process defined in claim 1 in which the dehydrogenation mixture is distilled to separate alphaisopropenylnaphthalene, beta-isopropenylnaphthalene and a mixture of alphaand betaisopropylnaphthalenes, and the mixture of alphaand :beta-isopropylnaphthalenes recycled for dehydrogenation with the alkylation reaction products.

3. A process of producing pure alphaand beta-isopropyl naphthalenes from a mixture thereof such as is obtained by alkylating naphthalene under high pressure with propylene in liquid phase at a temperature of 150 to 300 C. in the presence of an activated alumina-silica catalyst in which the beta-isopropyl naphthalene content is greater than 80%, comprising: diluting the mixture with an equal volume of a low boiling solvent, cooling the mixture to a temperature of 35 to 45 C. to crystallize beta-isopropyl naphthalene, separating the crystallized beta-isopropyl napthalene from the mother liquor, dehydrogenating the mother liquor nondestructively to form alpha-isopropenyl naphthalene, distilling the dehydrogenation product to recover alpha-isopropenyl naphthalene, hydrogenating the alpha-isopropenyl naphthalene under super-atmospheric pressure to produce alpha-isopropyl naphthalene, and distilling the hydrogenation product to recover a pured alpha-isopropyl naphthalene.

4. The process dened in claim 3 in which the low boiling solvent is a solvent of the group consisting of methanol, petroleum ether and parafn hydrocarbons having 3 to 7 carbon atoms.

5. A process of producing a mixture of alphaand beta-isopropylnaphthalenes in which the beta-isopropylnaphthalene constitutes from to of the mixture, comprising: dissolving one part of propylene in 3 to 10 parts of naphthalene and alkylating the naphthalene with the propylene under suiiicient pressure to maintain the products in liquid phase (300 to 900 lbs. per square inch) at a temperature of approximately 250 C. in the presence of an activated silicaalumina catalyst.

JOSEPH E. NICKELS.

REFERENCES CITED The following references are of record. in the OTHER REFERENCES Slanina et al., Organic Reactions with. Boron Fluoride, J. A. C. S., vol. 57, pages 1547-9 (September, 1935) 3 pages.

Zelinsky et al., Aromatization by Catalysis," Ind. Eng. Chem., vol. 27, pages 1209-11 (October, 1935), 3 pages.

Berichte, vol. 46, page 535 (1913), 1 page only.

Egloif, Physical Constants of Hydrocarbons, vol. 1V, pages 98, 99, 126, 127 (1947). 

1. A PROCESS OF PRODUCING SUBSTANTIALLY PURE ALPHA- AND BETA-ISOPROPYL NAPHTHALENES FROM A MIXTURE THEREOF SUCH AS IS OBTAINED BY: ALKYLATING NAPHTHALENE UNDER HIGH PRESSURE IN THE PRESENCE OF AN EXCESS OF PROPYLENE IN LIQUID PHASE AT A TEMPERATURE OF 150* TO 300* C. IN THE PRESENCE OF AN ACTIVATED ALUMINA-SILICA CATALYST COMPRISING: DEHYDROGENATING THE MIXTURE OF ALPHA- AND BETA-ISOPROPYL NAPHTHALENES NON- DESTRUCTIVELY TO PRODUCE A MIXTURE OF ALPHA-AND BETA-ISOPROPENYL NAPHTHALENES, DISTILLING THE MIXTURE TO SEPARATE ALPHA- AND BETA-ISOPROPENYL NAPHTHALENES AND SEPARATELY HYDROGENATING THE ALPHA- AND BETAISOPROPENYL NAPTHALENES TO RECOVER RESPECTIVELY ALPHA- AND BETA-ISOPROPYL NAPHTHALENES, AND PURIFYING THE ALPHA- AND BETA-ISOPROPYL NAPHTHALENE PRODUCTS SEPARATELY BY DISTILLATION 